1. Field of the Invention
The present invention relates to an illumination device applied to illuminate a license plate of a vehicle.
2. Description of the Related Art
As an illumination device for a license plate of a vehicle, such a system has broadly been utilized, where a light source is arranged at a position upward or obliquely upward of the license plate for irradiating the light emitted from the light source to the surface of the license plate. For the light source, bulbs (electric lamps) are ordinarily employed, but since the bulb does not have especial directivity, it cannot illuminate the surface of the license plate with a light of uniform illumination, so that this matter decreases recognition of letters or numerals shown on the license plate, and degrades the design characteristic.
On the other hand, a LED (light emitting diode) has been proposed to utilize to the light source because of merits of saving energy or having a long life. However, with the technical level of nowadays, a luminous flux as high as the bulb cannot be provided with one LED. Even if serving the highly brightened LED, similarly to the case of the bulb, there still remains a problem that difference in illumination appears in ranges near to and remote from the LED in the license plate. Although the illumination increases as a whole if increasing the using number of LEDs, there would be caused other problems such as limitation to positions of installing the LEDs or increasing in cost.
As the related art of the invention, refer to JP-UM-A-2-54745 and JP-UM-A-63-185745.
If lighting the whole of the license plate when employing the LED as the light source, it is considered to adjust the light emitting direction of the LED such that the LED's optical axis crosses with the center of the license plate. But, with such a structure, actually, the illumination is remarkably prominent around ranges near the LED, causing an irregularity of illuminance. On the other hand, if adjusting the light emitting direction of the LED such that the LED's optical axis crosses with a lower range than the center of the license plate, there increases the light not used to the illumination of the license plate, causing the illuminating effect reduced.
Further, in order to enhance the visibility of the license plate of the vehicle at night, the surface of the license plate is irradiated with light. According to this front light type lighting method, the license plate is directly irradiated with a light sent from the light source arranged in either an upper portion, a lower portion or a side portion of the license plate. In order to more excellently light the license plate, a method of using a reflector has been proposed (refer to JP-UM-A-2-54745). According to the method, not only the license plate is directly irradiated with a light emitted from the light source but also a region distant from the light source is irradiated with a light reflected on a reflector. Due to the foregoing, the overall surface of the license plate is uniformly irradiated with light so that the irregularity of illuminance may be reduced.
In order to enhance the design of an entire of the vehicle or each portion of the vehicle, there have been making every effort. Accordingly, even in a license plate section, not only it is necessary to enhance the visibility of the license plate at night but also it is required to enhance the design and the decoration of the license plate portion.
As a result of the investigation made in view of the above problems to be solved, in order to enhance the design, it is considered to be effective that not only the license plate is illuminated but also a light emitting portion is provided in the circumference of the license plate. For example, when a light emitting portion, the shape of which is the same as letters or a logotype mark, is provided on an observation face of a garnish for accommodating the light source of the license plate and this light emitting portion is made to emit light at night, the license plate portion can be decorated by the light emitting portion. However, in this case, it is necessary to provide another light source for supplying light to the light emitting portion arranged in the garnish. When it is considered that a space in the garnish is limited to be small, it is difficult to arrange another light source in addition to the light source for the license plate in the garnish. Further, to provide both light sources in the garnish is not preferable in view of the design. Furthermore, when two types of light sources are arranged in the limited space in the garnish, the assembling work becomes complicated.